Neutron irradiation effects on the infrared absorption of the<i>EL</i>2 defect in GaAs: New interpretation for the intracenter transition

Abstract

The effect of neutron irradiation on the optical properties of the EL2 center in semi-insulating GaAs was studied using the infrared absorption technique. The results show that the absorption band known as the intracenter transition between 1.03 and 1.27 eV is decreased by neutron irradiation. This absorption band is interpreted as a charge-transfer transition between the ${\mathrm{As}}_{\mathrm{Ga}}$ antisite and an X component(s) assuming that EL2\ensuremath{\equiv}${\mathrm{As}}_{\mathrm{Ga}+\mathrm{X}}$. The neutron irradiation increases the ${\mathrm{As}}_{\mathrm{Ga}}$ antisite concentration and reduces the EL2 concentration. The reduction of the EL2 concentration is due to the decrease of the X-component concentration. The zero-phonon line observed at 1.039 eV may not be an internal optical excitation within the isolated ${\mathrm{As}}_{\mathrm{Ga}}$ antisite.